Raising the standards

How nickel-containing stainless steel make food safer

December 21, 2016

A fifth of all nickel production is destined for food contact materials, primarily stainless steel, which because of its outstanding properties meets the stringent requirements of the industry. To ensure that food is completely safe, standards and guidelines for equipment must be adhered to. Yet there are many different standards, by different organizations, in different countries, with different approaches, even if they have the same ultimate goal. Some standards are mandatory, others are voluntary, and they are regularly updated to address new concerns.

Need for standards

One such concern arose in 2011 when the United States was subjected to a Listeriosis food poisoning outbreak. Thirty-three people died and there were 147 confirmed cases across 28 states. The incident was caused by the bacterium Listeria monocytogenes from contaminated cantaloupes and was linked to a single farm in Colorado. While foods made from raw milk, such as unpasteurized cheese, and ready-to-eat deli meats are known to have the potential to carry Listeria, fruits such as cantaloupe had not previously been identified as sources of concern.

Food and Drug Administration (FDA) officials had found Listeria at the farm in question on dirty, corroded equipment which had been previously utilised in potato farming. The FDA stated that the “equipment’s past use may have played a role in the contamination”. Water contaminated with Listeria was also found on the floor of the packing plant and it was determined that the workers moving around the plant had spread it, as the contaminated water was also found on the cantaloupe conveyor belt.

The FDA considered this Listeriosis outbreak to be “yet another reason to fully implement the Food Safety Modernization Act” (FSMA) which was signed into law on January 4, 2011. The Act aims to ensure the US food supply is safe by shifting the focus of federal regulators from responding to contamination to preventing it, and provides the FDA with the authority to require preventive controls across the food supply chain; perform inspections and ensure compliance; recall contaminated food and ensure imported foods meet US standards.

A stainless steel for every application

While FSMA does not place requirements on which materials should be used for food contact surfaces, other food industry standards such as 3-A clearly favour the use of nickel-containing stainless steel such as Type 304 (UNS S30400) or higher alloyed grades. These alloys are used to fabricate corrosion-resistant equipment and provide an infrastructure that can be easily cleaned and disinfected to prevent contamination such as Listeriosis. Stainless steels are widely used in abattoirs, and a whole host of food production applications, in farms for animal enclosures, feeding and watering stations, milking equipment and milk storage, as well as equipment to collect and treat animal wastes. There is an austenitic stainless steel for almost every food application, from milk and beer, where Type 304 has served the industry well for over 50 years; fish and meat products which may require a higher grade such as Type 316L (S31603); right through to the super-austenitic steels developed to cope with extremely aggressive conditions of soy sauce production.

Not just clean and shiny

When designing food-processing equipment, ‘hygienic’ does not simply mean ‘always clean and shiny’ but rather ‘resistant to the build-up of process soils and easy to clean between production runs.’ It is not just a matter of choosing materials which will not corrode or will not “impart their constituents to the food in quantities deleterious to human health” but ones which can be fabricated into the complex shapes and components such as a quadra-lobe fluid pump or a double mix-proof valve. Nickel-containing stainless steels meet these criteria and their formability, machinability and weldability allow their fabrication to fine tolerances both practicable and economically feasible


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